1. Field of the Invention
The present invention relates generally to manholes and storm drains and more particularly, to an improved manhole and storm drain assembly enabling ready vertical adjustment.
The common procedure practiced in the preparation of roadway access devices for resurfacing beings with removal of sufficient amount of the road composition surrounding the installed riser member. This necessitates the use of a jackhammer along with its compressor apparatus and entails a very time consuming operation as the entire periphery of the riser must be cleared of contact with road material and many risers present a height of 6 or more inches. The foregoing maneuver is required either when replacing the existing riser with a higher model or, before installing adaptor means or manipulating adjustment means to permit elevation of the same riser. After provision is made to modify the plane of the riser and its associated lid or cover, the readjusted assembly is grouted or otherwise sealed in order to fix it in position and to replace road material that had to be removed. It is not uncommon for the repositioning of a large drain or manhole assembly to require up to three men plus their heavy equipment and three hours' time before the road is ready to be resurfaced.
In view of the labor and time now required to ready existing manholes and storm drains for a resurfacing job, the public is often subjected to at least protracted inconvenience and frequently, less than safe driving conditions. This is evident when one considers that the time required to reposition the manholes and storm drains throughout a repaving job of several miles can very well result in many of the repositioned risers remaining in an exposed elevated condition for some time before repaving commences.
What is desirable in the adjustment of a riser is a minimal amount of necessary equipment or force and time. Another desirable feature is to completely eliminate the excavation that has to be done in order to clear the riser from the surrounding pavement so that it can be repositioned. Thus, a combination of these features can save many valuable manhours and expense in the resurfacing of roads, sidewalks and the like.
2. Description of the Prior Art
Asphalt and tar roads are periodically resurfaced every 5 to 7 years. This is due to the wearing away of the surface by the constant passing of traffic and this resurfacing of a road usually raises its height by about 2 inches. Manholes and storm drains which are disposed within the area of a road surface initially have to be raised before the road is resurfaced in order to keep their top openings and supported covers level with the road after it is resurfaced.
Numerous prior art devices have sought to address this issue of adjusting the manhole cover height. U.S. Pat. No. 4,325,405 issued to Christo discloses a telescopic riser used with gas and water mains that are placed in sidewalks. The device uses concentric tubes and screw threads to adjust the height of the riser. This device though does not allow for quick clearance of the surrounding sidewalk surface area. The immediate area must be excavated to clear away enough area for the riser to lift. This excavating can take quite a long time and if there are a number of such risers in place in the area to be resurfaced this adds considerable time to the overall job.
The vertical adjustment of manhole assemblies by the of various ring spacers is taught in U.S. Pat. No. 4,337,005 issued to LeBaron but wherein hoist means must be used to lift the device to allow snap ring(s) to move into position beneath a riser member. Obviously, precise vertical adjustment will not be possible and if the riser ring is lifted too far, an additional snap ring could snap into position beneath the riser ring and nothing short of a major excavation would be necessary to reinstall the entire assembly at a lower position.
Another telescopic manhole assembly is shown in U.S. Pat. No. 4,075,796 issued to Cuozzo and wherein vertical adjustment of a riser is achieved by rotation of the riser within the confines of its sole support comprising a threaded flange. Since the minimum wheel load requirements for a manhole cover and assembly is 16,000 pounds, his flange and threads are formed in a specific manner intended to resist such a load factor, a vast departure from the present invention wherein the weight of the riser as well as loads applied thereto are not transmitted to a threaded member but rather, to a conical riser surface supported by surrounding fixed material.
U.S. Pat. No. 3,390,224 issued to Wyatt also discloses a similar device that utilizes telescopic concentric tubes and mating screw threads to adjust the height. Again there is no clearance between the riser and the paved surface. Excavation must first be done to allow the riser to be lifted up and out. Another problem with this particular device is that it is merely a light-weight shell, incapable of standing up to the pressures that would be exerted by constant traffic.
The use of synthetic compositions to produce an underground enclosure as used in utility installations will be found in U.S. Pat. No. 3,974,599 issued to Grosh and which illustrates a main body member having a vertical wall. An adjustable cap device is provided with a likewise vertical skirt that surrounds the main body member in a spaced-apart relationship.
U.S. Pat. Nos. 3,629,981 and 4,075,796, issued to McCaffrey and Cuozzo respectively, provide manhole risers that have a vertically adjustable portion placed within an outer tube. Excavation would not be as necessary with these devices, but there is quite a bit of frictional force involved in raising these risers due to the substantial extent of the vertical contacting surfaces. Most likely the riser would have to be raised by a machine. In the Cuozzo patent the threads are merely left in a cast state, not further refined by machining. This would give a very high frictional force resisting any attempts at turning the riser.
U.S. Pat. No. 1,828,601 and 2,626,674 issued to Frye and Boosey respectively, depict further examples of drain fittings comprising a threaded top-most member threadedly cooperating with a relatively stationary element to permit relative vertical displacement therebetween.
None of the above prior art devices are seen to suggest the unique combination as offered by the instant invention and wherein a generally conical riser body supports the assembly, transmits applied loads to surrounding fixed material and permits ready elevation of the riser without any excavation of the surrounding material.